The invention relates to a medical instrument for the treatment of biological tissue.
Such instruments are used to accelerate or even initiate the process of healing broken bones and bone defects, but also paradontosis, by means of pressure or impact waves. Other fields of application are the treatment of chronic pains occurring with disorders of the point of attachment of sinews and the dissolution of myofascial trigger areas. It is assumed that the pressure waves cause microscopic damages to the biological tissue that cause the body to take regenerating actions.
Presently, so-called extracorporeal pressure or impact wave devices are used for such applications. These devices generate an acoustic pulse and pass it, via the skin surface, to the target region within the body, where it will then become effective. A device of this class of apparatus, which has a simple structure, is described in the patent document DE 197 25 477. Here, the acoustic pulse is generated by the impact of a projectile and is coupled unfocussed into the body via a blunt transmission element. Other medical devices of this type focus an acoustic pulse to the target region. A typical example of such a device can be found in the German Laid Open document DE 23 51 247. Here, a spark discharge serves as the source of the acoustic pulse which is focused by an elliptic reflector. For generating the pressure waves, prior art meanwhile also includes electromagnetic and piezoelectric sources (DE 35 02 751). Known alternative means for focusing are the use of acoustic liquid or solid matter lenses (U.S. Pat. No. 5,727,875), the design of the acoustic source as a moved spherical cap surface (DE 33 12 014 C2) or the disposition of a plurality of sources on a ball surface (DE 199 28 491 A1) as they are often used in piezoelectric drives.
The operation of all known focusing systems requires a high voltage power unit to generate the short but strong acoustic pulses. This makes the devices complicated, limits the maximum repetition frequency per unit time with a still reasonable structural size, and requires safety measures for isolating the high voltage. The embodiments of DE 197 25 477 do not allow a focusing of the acoustic energy and applications are thus restricted to indications close to the surface.